1. Field of the Invention
The present invention relates to a dielectric ceramic composition, an electronic component and manufacturing method thereof, more particularly, for a non-reducing compensating temperature dielectric ceramic composition suitable for an electronic component such as a multilayer ceramic capacitor wherein an internal electrode is a base metal.
2. Description of the Related Art
A multilayer ceramic capacitor is widely used as an electronic component, and large numbers of electronic components are used in one electronic device. Normally, a multilayer ceramic capacitor is produced by stacking an internal electrode layer paste and an external electrode layer paste by the printing method or the sheets method or so and by cofiring thereof.
In the meantime, the dielectric ceramic material used for a conventional multilayer ceramic capacitor has a property that it is reduced when it is fired in a reducing atmosphere and becomes semiconductor. Therefore, as for the internal electrode material, a precious metal such as Pd or so has been used since those do not melt at a temperature in which a dielectric ceramic material is sintered, and also do not oxidize even it is fired under a high oxygen partial pressure in which the dielectric ceramic material does not become a semiconductor.
However, the precious metal such as Pd or so is expensive, thus it becomes a big problem for price reduction of the multilayer ceramic capacitor. Thus, as for the internal electrode material, the use of comparatively inexpensive base metals such as Ni or Ni alloy has become a main stream.
However, in case the base metal is used as a conductive material of the internal electrode layer, the internal electrode layer is oxidized when it is fired in the air. Thus, it is necessary to perform the cofiring of the dielectric layer and the internal electrode layer in a reducing atmosphere.
However, when the firing is performed in the reducing atmosphere, an insulation resistance is reduced since the dielectric layer is reduced. Therefore, a non-reducing dielectric material is proposed. However, a multilayer ceramic capacitor using non-reducing dielectric material had a problem of decrease in an insulation resistance (IR) by reliability test, when a thickness of a dielectric layer is made thin (5 μm or less).
Also, due to the rising demand for a temperature compensation dielectric ceramic composition having a small temperature change of the capacitance, namely, a capacitance temperature coefficient is small and possible to control arbitrarily within a range of −150 to +150 ppm/° C., there is a need for a ceramic composition which is available to provide such capacitor having controllable low temperature coefficient.
In order to meet such demand, in Patent Document 1 (WO2004/063119) discloses a dielectric ceramic composition comprises at least;
a main component including a dielectric oxide of the composition shown by[(CaxSr1-x)O]m[(TiyZr1-y-zHfz)O2]
a first subcomponent including Mn oxide and/or Al oxide, and
a glass component, wherein;
symbols m, x, y and z of compositional molar ratios included in said main component are in relation with;
0.90≦m≦1.04,
0.5≦x<1,
0.01≦y≦0.10, and
0<z≦0.20.                Further, according to Patent Document 1, Mn oxide may be added to said dielectric ceramic composition, and the amount thereof is 0.2 to 5 mol % in terms of MnO with respect to 100 mol % of the main component.        
According to the dielectric ceramic composition of Patent Document 1, a non-reducing dielectric ceramic composition with a high reliability can be realized, which is preferably used as a dielectric layer of the multilayer ceramic capacitor using a base metal such as Ni or so as an internal electrode, possible to sinter at 1300° C. or lower, having a small temperature coefficient of the capacitance, possible to arbitrarily control within a range of −15 to +150 ppm/° C., having the insulation resistance 1×10−13Ω or more at 25° C., having a small frequency dependency of a specific permittivity and dielectric loss tangent (tan δ), having a long acceleration life time of the insulation resistance even when a dielectric layer is made thin, and small defective ratio of the insulation resistance.